Latching-type digital phase shifter employing toroids of gyromagnetic material



Nov. 28, 1967 D. R. TAFT 3,355,682

LATCHING-TYPE DIGITAL PHASE SHIFTER EMPLOYING TOROIDS OF GYROMAGNETICMATERIAL Filed on. 21, 1965 TO CURRENT CONTROL SOURCE FIG.42.

WINDING SQUARE LOOP GYROMAGNETIC DIELECTRIC MATERIAL MAGNETIZINGWlNDINGS 280 DEMAGNETIZING FIG.1.

INVENTOR. 00mm TAFF A TTOR/VEY WINDING I United States PatentLATCHllNG-TYPE DIGITAL PHASE SHIFTER EM- PLUYING TOROIDS 0F GYRUMAGNETICMA- TERIAL Donald R. Taft, Dunedin, Flap, assignor to Sperry RandCorporation, a corporation of Delaware Filed Oct. 21, 1965, Ser. No.499,868 9 Claims. (Cl. 333-31) ABSTRACT OF THE DISCLOSURE A microwave,digital, reciprocal phase shifting apparatus comprising a gyromagneticmember disposed symmetrically within a wave propagating medium in aregion where the magnetic field of the electromagnetic wave is linearlypolarized, the gyromagnetic member being oriented such that an axis ofsymmetry passing through an aperture in the member is transverse to thedirection of wave propagation. Current alternately applied to anelectrical conductor threading the aperture and another conductortraversing the gyromagnetic member in the direction of wave propagationestablishes orthogonal magnetic fields which cause the member to presenttwo discrete values of permeability to the electromagnetic wave.

This invention relates to electromagnetic wave phase shifting devicesand more particularly relates to small and efficient reciprocallatching-type digital phase shifters that utilize toroids ofgyroinagnetic material whose magnetization states may be selectivelyswitched to provide different values of phase shift, and which requireno external magnetizing energy to maintain either value of phase shift.In the present invention the toroids are so positioned in the magneticfield of the electromagnetic waves and their magnetization states arechosen so as to assure optimum interaction with the linearly polarizedmagnetic field components when magnetized in one state and to provideminimum interaction with said components when magnetized in their secondstate, thus providing large differential phase shifts.

Phase shifters constructed in accordance with the present invention areparticularly useful in the so-called digital phase shifters that havebeen proposed for use in radar systems whose antenna beams are to beelectronically scanned. Electronic scanning is achieved by providing aplurality of wave radiating elements whose relative physicalarrangement, together with their amplitude and phase of excitation, areso proportioned that the composite radiation pattern of all the elementsis a shaped beam whose direction in space may be changed in a controlledmanner. A rather complex waveguide network having a plurality of wavepropagating paths connects the microwave transmitter to the variousradiating elements and establishes the required amplitude and phaserelationships at the elements. The beam is continuously scanned in smallangular increments by changing in discrete steps the phase shift of thewaves through the various paths of the waveguide network. It is obviousthat in order to effectively cover a large volume of space with arapidly scanned antenna beam, the phase shifting means in the waveguidenetwork must be capable of rapidly changing in discrete steps the phaseof the electromagnetic waves through the various paths of the network.Further, because a large beam-scanning radar system may employ hundredsor thousands of phase shifting devices in the waveguide network, theswitching power that is required to effect phase changes in all of thephase shifting devices is a matter of primary concern and must be heldto a minimum.

In designing the waveguide networks for use in these types of radarsystems, considerable attention has been given to the use of phaseshifters that employ gyromagnetic materials. These phase shifters of thedigital type employ several members of gyromagnetic material, eachmember having its own independent. magnetizing source. Most commonly, amagnetizing source functions to magnetize each gyromagnetic member toone or the other of two magnetization states. The individual members ofgyrornagnetic material introduce different values of phase shift bythemselves, and by selectively magnetizing various combinations of theindividual members to one or the other magnetization state, differentvalues of phase shift may be selected. In order to reduce the powerrequirements of the magnetizing sources, gyromagnetic members in theshape of toroids, and having two remanent magnetization states, havebeen used. This then requires magnetization power only during theswitching operation, and no source power is required to hold a toroid ina given one of its remanent magnetization states. Phase shiftersoperating in this manner sometimes are called latching phase shiftersbecause the toroids of gyromagnetic material always are used in one orthe other of their magnetization states.

When used in beam scanning radar systems it is desirable that the phaseshifters be reciprocal, or bilateral, in their operation because inorder for the antenna to receive reflected waves from the same directionin which they were radiated during transmission, the various paths ofthe waveguide network must be the same electrical length for both thetransmitted and received waves. To achieve bilateral operation, thetoroids of ferrimagnetic material should be positioned in thetransmission lines of the waveguide network in regions where themagnetic fields of the transmitted and received waves are linearlypolarized. In magnetizing toroids of ferrimagnetic material to obtaindifferent values of phase shift from each toroid, it will not bepossible to switch the magnetization states between the two remanentmagnetizations of a square hysteresis loop magnetization characteristicbecause this would result inthe same magnitude of phase shift for bothmagnetizations. Consequently, other combinations of magnetizationconditions must be utilized in switching the toroids to producedifferent values of bilateral phase shift.

It therefore is an object of this invention to provide anelectromagnetic wave reciprocal phase shifter employing gyromagneticmaterial whose magnetization may be switched between two states thatprovide substantially optimum and substantially minimum interactionbetween the material and the waves.

Another object of this invention is to provide in an electromagneticwave reciprocal phase shifter means for selectively magnetizing a toroidof gyromagnetic material in either one of two orthogonal directions,whereby the material introduces different values of reciprocal phaseshift when magnetized in the different directions.

In accordance with the present invention a reciprocal latching typephase shifter is constructed in a double ground plane strip transmissionline by providing a plurality of toroids of gyromagnetic material eachof which is disposed symmetrically within the transmission line with thecenter axis of its aperture extending transversely to the centerconductor of the line and parallel to the ground plane conductors. Eachtoroid has a square hysteresis loop magnetization characteristic thatincludes two opposite remanent magnetization states. The center stripconductor of the transmission line extends through each toroid fromfront-to-back and thus transversely to the axis of the toroid aperture.A magnetizing winding threads each toroid aperture and serves: tomagnetize the toroid in a circumferential direction to one of itsremanent magnetization states. Because the toroid is located in a regionwhere the magnetic field components of the electromagnetic waves arelinearly polarized, and because the toroid is everywhere magnetizedtransversely to those magnetic field components, the gyromagneticmaterial interacts optimally with the electromagnetic waves and producesa relatively large value of phase shift. To obtain a different value ofphase shift from each toroid, a magnetizing current pulse is passedthrough the portion of the center strip conductor that extends throughthe toroid. The toroid then is magnetized in a circular direction thatis orthogonal to its first direction of magnetization. In this secondcondition of magnetization the magnetic moments of the material aresubstantially parallel to the direction of the linearly polarizedmagnetic field components of the electromagnetic waves and there isminimum interaction between the material and the waves, thus resultingin a minimum value of phase shift to the waves. Each individual toroidproduces a different value of maximum phase shift and the magnetizationstate of each toroid is independently controllable. By selectingdifferent magnetization states for various toroids different values ofphase shift may be produced. Because the material interacts optimallywith the electromagnetic waves when magnetized in one condition andinteracts minimally when magnetized in the other state, a minimum amountof material need be utilized in the toroids. This feature, together withthe requirement for magnetizing current only during the switching ofmagnetizations, provides small and efficient reciprocal latching-typephase shifters.

The invention will be described by referring to the accompanyingdrawings wherein:

FIG. 1 is a simplified illustration of a latching-type digital phaseshifter constructed and operated in accordance with the presentinvention; and

FIG. 2 is a sketch showing a toroid of gyromagnetic material and is usedto explain the different magnetization states of the toroid.

Referring now in detail to FIG. 1, a double ground plain striptransmission line is comprised of the broad conductive ground planes 11and 12 and the narrow center strip conductor 13 which is disposedsymmetrically between said ground plane conductors. A strip transmissionline-to-coaxial transmission line transition member 14 provides meansfor coupling strip transmission line 10 to a coaxial input connector 15.A similar arrangement is provided at the opposite end of the device by atransition member 16. Strip transmission line 10 propagateselectromagnetic waves in a TEM mode in which the electric field extendstransversely between the center strip conductor 13 and the respectiveground planes 11 and 12. The magnetic field lines of this TEM mode arein the form of ellipses that extend circumferentially about center stripconductor 13, and the components of this magnetic field aresubstantially linearly polarized in the region about center stripconductor 13.

Center strip conductor 13 extends longitudinally and symmetricallythrough the two toroidally shaped members 19 and 20 of gyromagneticmaterial. The toroids 19 and 20 of gyromagnetic material are positionedwithin strip transmission line 10 so that axes of symmetry passingthrough their toroidal apertures 22 and 23 are transverse to thelongitudinal axis of strip transmission line 10 and parallel to theground plane conductors 11 and 12. The toroids 19 and 20 have squarehysteresis loop magnetization characteristics and may be comprised ofany of the suitable ferrimagnetic materials that are known to thoseskilled in the art. In a practical latching-type digital phase shifterintended for use in electronically scanned radar systems more than twotoroids most likely would be used, but for simplicity of illustrationand description, just two toroids have been illustrated in FIG. 1. Themagnetizing windings 26 and 26 thread the respective apertures 22 and 23in toroids 19 and 20 and serve to magnetize the toroids in acircumferential direction around their toroidal shape as illustrated inFIG. 2. Pulses of magnetizing currents are supplied to the windings 26and 26' by the respective magnetizing current sources 27 and 27. Theconductors 28a and 28b each contact the portion of center stripconductor 13 that passes through toroid 19 and thereby establishes asecond magnetizing current path which will be referred to hereinafter asthe demagnetizing winding. The conductors 29a and 2% are similarlyconnected and serve the same purpose with respect to toroid 20.

In order to provide D.C. isolation for the two demagnetizing windingsjust described, appropriate D.C. blocking capacitors are provided incenter strip conductor 13. Two of these capacitors are illustrated bythe members 32 and 33. As may be seen from the cut-away view of themember 32, an outer cylindrical shell 34 is conductively secured to theleft end of center strip conductor 13 and is provided with an insulatingsleeve 35 about its inner surface. The portion of center strip conductor13 within the sleeve 35 is fashioned to make a snug fit within thesleeve and nowhere contacts the conductive cylinder 34 on the left endof center strip conductor 13. Thus, an open circuit is established forDC. currents but a relatively large A.C. capacitance is formed so as toprovide negligible disturbance to A.C. currents propagating on the striptransmission line. The magnetizing current sources 27 and 27 applyappropriate magnetizing and demagnetizing current pulses to therespective windings associated with each of the toroids 19 and 20 so asto change the magnetization states of the toroids in response to commandsignals on the respective lines 38 and 39 which may be coupled to acurrent control source whose operation may in turn be controlled bylogic or computer apparatus which programs the magnetization states ofthe toroids of all of the phase shifters of a radar system to achievethe desired scanning of an antenna beam. In practice, each phaseshifting device 10 may include four toroids which respectively producedifferential phase shifts of 22.5", 45, and By selectively choosingdifferent magnetization states of the four toroids, differential phaseshifts in increments of 22.5 may be selected from 0 to 360.

In the operation of a digital phase shifter it is required that theferrirnagnetic material produce two different values of phase shift whenin two different magnetization states. The different values of phaseshift result from the fact that the ferrirnagnetic materials presentdifferent values of permeability to the electromagnetic waves when inthe two different magnetization states. To assure that the phase shifterfunctions in a reciprocal manner the magnetic field components of theelectromagnetic waves that propagate in opposite directions through theferrimagnetic material must be linearly polarized. To add assurance thatthis condition is in fact achieved in the device of FIG. 1, slabs 40, 41and 42, 43 of a low loss, non-magnctic dielectric material having arelative dielectric constant substantially the same as that of thetoroids of ferrimagnetic material are respectively positioned along thesides of the toroids 19 and 20. The function served by the slabs 49-43of dielectric material is to present at the sides of the toroids 19 and20 a medium having the same dielectric constant so that the magneticfield lines of the electromagnetic waves are not disturbed at the sideboundaries and thus the field in this region will be substantiallypurely linearly polarized rather than tending to become ellipticallypolarized at the boundaries as they would if a different dielectricconstant medium were present. Further, for the ferrimagnetic material tointeract in an optimum manner with the magnetic field of theelectromagnetic waves, it is necessary that the material be magnetizedin a direction transverse to the direction of the magnetic fieldcomponents of the waves. Should the material be magnetized parallel tothe direction of the magnetic field components of the electromagneticwaves, the magnetic susceptibility of the material will be substantiallyzero and there will be minimum interaction between the ferrimagneticmaterial and the waves. These two facts are taken advantage of in theconstruction and operation of the phase shifter illustrated in FIG. 1,as will be explained in more detail with the aid of FIG. 2.

The linearly polarized magnetic field components of the electromagneticwaves are illustrated in FIG. 2 by the ellipses in formed by the brokenlines. To achieve one magnetization state of the toroid 19, amagnetizing current pulse is passed through winding 26 which establishesa magnetization flux in a circumferential direction about the toroidaperture 22 and magnetizes toroid 19 to a remanent magnetization state.The direction of magnetization of toroid 19 is illustrated in FIG. 2 bythe solid arrows about aperture 22. It may be seen that the magneticfield Components of the waves are everywhere transverse through thetoroid 19 and are everywhere transverse to the direction ofmagnetization of the toroid. Therefore, optimum interaction will takeplace between the ferrimagnetic material of toroid 19 and the magneticfield components of the electromagnetic waves. Because the magneticfield components of electromagnetic waves are linearly polarized, thesame interaction will take place irrespective of the direction ofpropagation of the Waves through the toroid 19 and the resulting phaseshift Will be bilateral. To obtain a different value of phase shift fromthe toroid 19, a magnetizing current pulse is passed through thedemagnetizing circuit comprised of the leads 23a, 28b and the portion ofcenter strip conductor 13 that extends through toroid 19. The DC.current pulse through the portion of center strip conductor 13establishes a magnetizing flux that magnetizes toroid 19 in acircumferential direction around center strip conductor 13, asillustrated by the curved solid arrows on the front face of toroid 19.With this condition of magnetization the ferrimagnetic material ismagnetized in directions substantially parallel to the directions of themagnetic field components of the electromagnetic waves. With thiscondition existing, the permeability of the ferrimagnetic material isessentially a scalar of value 1 and the magnetic susceptibility isnearly zero. Therefore, the interaction between the magnetic moments ofthe ferrimagnetic material and the magnetizing field component of theelectromagnetic waves will be substantially minimum and the interactionmay be considered essentially the same as if the ferrimagnetic materialwere demagnetized. Again, the conditions for reciprocal operation existand the two different conditions of magnetization would produce twodifferent values of phase shift for waves propagating through thedevice. In a practical latching-type digital phase shifter which employsfour toroids of ferrimagnetic material in the manner mentioned above,each toroid would produce a different magnitude of differential phaseshift, and by appropriate energization of the magnetizing anddemagnetizing windings of each toroid, different combinations of totalphase shift may be selected.

It will be understood that the teachings of the present invention alsomay be adapted for use in a coaxial transmission liue. In such a device,the inner conductor of the coaxial line would pass longitudinallythrough each one of the successively positioned toroids. In such adevice the toroids may have circular shapes in planes taken trans-;ersely to the longitudinal axis of the coaxial transmission While theinvention has been described in its preferred embodiments, it is to beunderstood that the words which have been used are words of descriptionrather than limitation and that changes within the purview of theappended claims may be made without departing from the true scope andspirit of the invention in its broader aspects.

What is claimed is:

1. In an electromagnetic wave device employing a member of gyromagneticmaterial and operating to have the magnetization state of said memberswitched between two diiferent magnetization states to eifectdifferential interaction with linearly polarized electromagnetic waveswhen in the two different magnetization states, the combinationcomprising:

electromagnetic wave propagating means for propagating electromagneticwaves along a given direction in a mode in which the magnetic fieldcomponent is linearly polarized in a given region,

a member of gyromagnetic material that exhibits gyromagnetic effects tosaid waves,

said member being positioned in said given region such that an axis ofsymmetry of said member is transverse to said given direction andsubstantially coincident with the axis of an aperture in said member,

first means for magnetizing said member in a first direction around saidaxis, whereby said member presents a first value of permeability to saidwaves, and

second means for magnetizing said member in a second directionorthogonal to said first direction so that said member presents a secondvalue of permeability to said Waves,

said first and second means being actuated alternately to switch themagnetization of said member between said first and second directions.

2. The combination claimed in claim 1 wherein:

said means for magnetizing said member in said first direction is afirst current conductor that threads said member in the direction ofsaid axis of symmetry, and wherein,

said means for magnetizing said member in said second direction is asecond current conductor that threads said member in a directionorthogonal to said axis of symmetry.

3. The combination claimed in claim 2 wherein said electromagnetic wavepropagating means is comprised of a TEM mode transmission line having atleast first and second conductors extending in said given direction,

said second conductor extending through said member and serving as saidsecond current conductor.

4. The combination claimed in claim 3 wherein said TEM mode transmissionline is a coaxial transmission line and said second conductor is theinner conductor of said coaxial transmission line.

5. The combination claimed in claim 1 wherein said member has arectangular cross-section and further including:

low loss, non-magnetic dielectric material disposed along said member ofgyromagnetic material on the sides thereof oriented transverse to saidaxis of symmetry, said material having a dielectric constantsubstantially the same as that of the gyromagnetic material, thereby toassure that said magnetic field component is linearly polarizedthroughout the entire region occupied by said member.

6. An electromagnetic wave phase shifter comprising:

a strip transmission line comprised of a narrow strip conductor and apair of broad conductive ground plane conductors spaced from andextending parallel to said strip conductor,

a plurality of longitudinally disposed members of gyromagnetic materiallocated entirely between said ground plane conductors with respectiveaxes of symmetry passing through an aperture in each of said membersbeing transverse to said strip conductor, and with said strip conductorextending successively through each of said members,

means for magnetizing each of said members in a first direction aroundits respective axis of symmetry, and

means for magnetizing each of said members in a second direction aroundsaid strip conductor,

said members being alternately magnetized in either of said first andsecond directions.

7. An electromagnetic wave device comprising:

a longitudinally extending strip transmission line comprised of a pairof broad conductive ground plane conduetors disposed in spaced parallelrelationship and a narrow strip conductor disposed between said groundplane conductors,

a plurality of members of gyromagnetic material successively disposedalong said strip transmission line entirely between said ground planeconductors such that an axis of symmetry passing through an aperture ineach of said members is transverse to said strip conductor and parallelto said ground plane conductors,

said members each having a square hysteresis loop magnetizationcharacteristic,

said strip conductor extending longitudinally through each of saidmembers,

means for independently magnetizing each one of said members in a firstdirection around its respective axis of symmetry, and

means for independently magnetizing each one of said members in a seconddirection around the strip conductor that passes therethrough,

said members being alternately magnetized in either of said first andsecond directions.

8. The combination claimed in claim 7 wherein the 8 means forindependently magnetizing each of said members in a second directioncomprises:

means for passing magnetizng currents through those portions of saidstrip conductor which pass through said members.

9. The combination claimed in claim 7 wherein said member has arectangular cross-section and further including:

low loss, non-magnetic dielectric material disposed along said membersof gyrornagnetic material on the sides thereof oriented transverse tosaid axes of symmetry, said material having a dielectric constantsubstantially the same as that of the gyromagnetic material.

References Cited UNITED STATES PATENTS 2,994,841 8/1961 Zaleski 333-24.13,277,401 10/1966 Stern 333-241 ELI LIEBERMAN, Primary Examiner. HERMANKARL SAALBACH, Examiner.

P. L. GENSLER, Assistant Examiner.

1. IN AN ELECTROMAGNETIC WAVE DEVICE EMPLOYING A MEMBER OF GYROMAGNETICMATERIAL AND OPERATING TO HAVE THE MAGNETIZATION STATE OF SAID MEMBERSWITCHED BETWEEN TWO DIFFERENT MAGNETIZATION STATES TO EFFECTDIFFERENTIAL INTERACTION WITH LINEARLY POLARIZED ELECTROMAGNETIC WAVESWHEN IN THE TWO DIFFERENT MAGNETIZATION STATES, THE COMBINATIONCOMPRISING: ELECTROMAGNETIC WAVE PROPAGATING MEANS FOR PROPAGATINGELECTROMAGNETIC WAVES ALONG A GIVEN DIRECTION IN A MODE IN WHICH THEMAGNETIC FIELD COMPONENT IS LINEARLY POLARIZED IN A GIVEN REGION, AMEMBER OF GYROMAGNETIC MATERIAL THAT EXHIBITS GYROMAGNETIC EFFECTS TOSAID WAVES, SAID MEMBER BEING POSITIONED IN SAID GIVEN REGION SUCH THATAN AXIS OF SYMMETRY OF SAID MEMBER IS TRANSVERSE TO SAID GIVEN DIRECTIONAND SUBSTANTIALLY COINCIDENT WITH THE AXIS OF AN APERTURE IN SAIDMEMBER, FIRST MEANS FOR MAGNETIZING SAID MEMBER IN A FIRST DIRECTIONAROUND SAID AXIS, WHEREBY SAID MEMBER PRESENTS A FIRST VALUE OFPERMEABILITY TO SAID WAVES, AND SECOND MEANS FOR MAGNETIZING SAID MEMBERIN A SECOND DIRECTION ORTHOGONAL TO SAID FIRST DIRECTION SO THAT SAIDMEMBER PRESENTS A SECOND VALUE OF PERMEABILITY TO SAID WAVES, SAID FIRSTAND SECOND MEANS BEING ACTUATED ALTERNATELY TO SWITCH THE MAGNETIZATIONOF SAID MEMBER BETWEEN SAID FIRST AND SECOND DIRECTIONS.